With the advancement of assay, analysis, and examination techniques in recent years, various substances have been becoming measurable. Particularly, in the field of clinical examination, with the development of measurement principle based on specific reactions such as biochemical reaction, enzyme reaction, or immune reaction, substances in body fluids that reflect on condition of a disease became measurable.
Point of Care Testing (POCT) has been receiving attention particularly. POCT aims for simple and quick measurement in the first place, and for reduction in time it takes from sample taking to obtaining examination result. Therefore, for POCT, simple measurement principle is necessary. Also, there has been a demand for a measurement device which is small, easy-to-carry, and easy-to-operate.
In recent measurement devices for POCT, simple measurement principle has been developed. With such developments, techniques for solidifying a biological component, sensor device making, sensor system making, microfabrication, and micro fluid control are advancing. Thus, highly practical measurement devices have been increasingly provided.
For such measurement devices for POCT, for example, Patent Document 1 has proposed a device for qualitative and quantitative analysis of a sample supplied on the disc. The measurement device of Patent Document 1 is described with reference to FIG. FIG. 9 is a schematic cross sectional view of a portion of a chamber in an analysis disc. The disc 1 is provided with the sample supply hole 2 and the flow path 3 communicating with the sample supply hole 2. To the flow path 3, the reagent 4, which changes its optical property (transmittance, color, and the like) by reacting with the sample 5, is applied. The sample 5 is supplied from the sample supply hole 2 into the disc 1 and then analysis is carried out.
FIG. 10 is a schematic perspective view of an analysis device using the disc 1 of above, with a partially transparent view. Configuration of this analysis device is similar to the so-called optical disc device, the analysis device comprising the spindle motor 6 for spinning the disc 1; the optical pick-up 7 for applying a light beam to the sample 5 supplied and spread in the disc 1 or to the reagent 4 reacted with the sample 5; and the feed motor 8 for moving the optical pick-up 7 in the radial direction of the disc 1.
The disc 1 mounted in the analysis device is spun by the spindle motor 6. The sample 5 is supplied and spread in the flow path 3 of the disc 1 with the centrifugal force, to react with the reagent 4 applied in the flow path 3. After the reaction, a light beam is applied to the sample 5 or the reagent 4 in the flow path 3 by the optical pick-up 7, while the disc 1 is being spun. By detecting the reflected light or transmitted light of the light beam, reaction of the reagent is analyzed.
Patent Document 2 has proposed, for example, providing a flow path for connecting a plurality of chambers to which the reagent is applied in the disc. In this way, function of moving and stopping the sample mixture liquid freely between the chambers can be added to the disc. Thus, a plurality of reagents can be dissolved and reacted in order.
The sample-liquid analysis disc having a configuration of a microfluid device, proposed by Patent Document 2, is described briefly with reference to FIG. FIG. 11 is a diagram prepared by the inventors of the present invention for describing the technique described in Patent Document 2. FIG. 11 is a schematic view illustrating a relevant part of the disc included in the device proposed in Patent Document 2, in the direction of the normal to the main surface of the sample-liquid analysis disc. In FIG. 11, the flow path 12, bending, is connected to the lower side 11a of the upstream-side chamber 11, relative to centrifugal force direction X of the disc. The bending portion 12a of the flow path 12 is located at a position higher than the upper-side wall face, relative to centrifugal force direction X of the upstream-side chamber 11. The flow path 12 downstream of the bending portion 12a extends downward relative to centrifugal force direction X, and connected to the downstream-side chamber 13.
The downstream-side chamber 13 is connected to the transmitted light measurement chamber 15 by the flow path 14, also bending similarly to the flow path 12. The depth of the upstream-side chamber 11 in the direction of normal to the main surface is larger than the depth of the flow path 12. Thus, the sample mixture liquid that has been moving toward the downstream-side chamber 13 in the flow path 12 with capillarity accumulates at the portion where the flow path 12 is connected to the downstream-side chamber 13. As a result, the sample mixture liquid headed from the upstream-side chamber 11 to the downstream-side chamber 13 can be stopped at the point right before the downstream-side chamber 13.
By applying the centrifugal force by spinning the disc under such condition, the sample mixture liquid standing still flows into the downstream-side chamber 13. The bending portion 12a of the flow path 12 is located at a position higher than the upper-side wall face as noted above, relative to centrifugal force direction X of the upstream-side chamber 11. The flow path 12 downstream of the bending portion 12a extends downward, relative to the centrifugal force direction. With such a configuration, when the centrifugal force is applied, siphon effect comes into play on the sample mixture liquid accumulated in the upstream-side chamber 11 and filling the flow path 12 up to the point right before the downstream-side chamber 13, and almost all amount of the sample mixture liquid accumulated in the upstream-side chamber 11 flows into the downstream-side chamber 13 via the flow path 12.
While the centrifugal force is in effect, the sample mixture liquid that flowed into the downstream-side chamber 13 also flows into the flow path 14, but when seen in centrifugal force direction X, the liquid level in the flow path 14 and the liquid level in the downstream-side chamber 13 are the same.
Thus, as in the case of the flow path 12 described above, when the bending portion (not shown) of the flow path 14 is located at a position higher than the upper-side wall face of the downstream-side chamber 13, while the centrifugal force is in effect, the sample mixture liquid does not move to the point right before the next chamber (transmitted light measurement chamber 15).
The centrifugal force effect is lost when the spinning of the disc is stopped. At this time, from the flow path 14, the sample mixture liquid reaches the point right before the transmitted light measurement chamber 15 by capillarity. When the disc starts spinning again afterwards, with the effect of the centrifugal force, the sample mixture liquid flows into the transmitted light measurement chamber 15.
When the spinning of the disc (centrifugal force effect) is stopped, the sample mixture liquid in the transmitted light measurement chamber 15 may flow backward into the flow path 14 by capillarity. The backflow causes the amount of the sample mixture liquid in the transmitted light measurement chamber 15 to be insufficient; therefore, the centrifugal force is brought into effect by spinning the disc also when measuring the transmitted light.
For smooth flow of the sample mixture liquid into the chambers 11, 13, and 15, air holes 16, 17, and 18 are provided, at an upper portion (relative to centrifugal force direction X) of each of the chambers 11, 13, and 15 where the sample mixture liquid does not reach. In this way, the sample mixture liquid and the reaction reagent can be sufficiently dissolved and reacted. Also, the smooth movement of the sample mixture liquid can also be achieved in the flow path.
The reaction reagent necessary for the measurement of the specific component in the sample mixture liquid is carried in the upstream-side chamber 11, for example by drying. In this case, a reaction reagent layer is formed, by dropping and drying the aqueous solution of the reagent having at least a reagent concentration necessary for the reaction in a volumetric capacity of the upstream-side chamber 11; or by dropping and drying the aqueous solution of the reagent in an amount and a concentration that allow the reagent to be carried in an amount necessary for the reaction in the upstream-side chamber 11 when the reaction reagent is dissolved in the sample mixture liquid of an amount of the volumetric capacity of the upstream-side chamber 11.
It has also been proposed that the reaction reagent is solidified by freeze-drying the reagent solution, to improve solubility. For example, Patent Document 3 has proposed dropping the reagent solution in a refrigerating agent such as liquid nitrogen to obtain a spherical frozen material, and freeze-drying the spherical frozen material, to obtain homogenous reagent granules.
Patent Document 4 has proposed removing hemocyte by centrifugal separation in a blood measurement, to allow only the plasma component in blood to react with the reagent. The device described in Patent Document 4 has a function of separating plasma from whole blood by centrifugal force, and has a rotor for centrifugal separation, an inner chamber, a plurality of concave portions for testing, and a pathway. By disposing for example spherical granular reagent in the rotor for centrifugal separation, quick dissolution of reagent, that is, excellent reactivity can be achieved. For the reagent, in view of shelf life, granular reagent formed by freeze-drying can also be used.
With this device, a liquid sample can be supplied in stages. In this way, the measurement can also be carried out for the case when a plurality of reactions between the solid reagent and the liquid sample are carried out not simultaneously but in stages, and when the solid reagent has to be used in a plurality of kinds.
Patent Document 1: WO0026677
Patent Document 2: Japanese Unexamined Patent Publication No. 2002-534096
Patent Document 3: Japanese Patent No. 3187835
Patent Document 4: U.S. Pat. No. 5,122,284